1. Field of the Invention
The present invention relates to a canopy for a paraglider and a parachute, and, more particularly, to an arrangement of partition walls in the canopy.
2. Background
Recently, it has become popular to glide in the air using a paraglider and to skydive using a parachute having a construction similar to that of the paraglider.
FIG. 3 illustrates such a paraglider. The paraglider comprises a canopy 10, suspension cords 11 and a harness 12. The canopy 10 includes an upper side and a lower side to form an inflatable body 13. The body 13 is divided into a plurality of small chambers 15, referred to as reams or cells, by partition walls 14 which extend between the upper and lower sides of the canopy 10 at predetermined intervals along a span of the canopy. As can be seen in FIG. 4 , the partition walls 14 have a wing-like shape and extend from a leading edge of the canopy 10 to a trailing edge thereof. The partition walls are commonly referred to as ribs.
A plurality of air intakes 16 through which the air is introduced to inflate the canopy 10 are disposed at the leading edges of the respective cells 15. The canopy 10 inflated by the introduced air is maintained in a proper wing-like shape by virtue of the pressure of the introduced air and the wing-like shape of the partition walls 14. According to this arrangement, since an aerodynamic lift acts on the inflated canopy 10, a flyer can glide in the air using the paraglider. As can be understood, the partition walls 14 are important in maintaining the canopy 10 in the proper wing-like shape.
Next, a conventional partition wall 14 will be described with reference to FIG. 4 . An air impermeable material is used for the partition walls 14 as well as for the inflatable body 13. The materials consist of, for example, a cloth made by impregnating with synthetic resins a woven fabric made of synthetic fibers such as polyester fibers and polyamide fibers, or a cloth made by laminating a synthetic resin film onto at least one surface of the woven fabric. The cloth is required to be light weight yet strong. Generally, a cloth having 45-50 g/m.sup.2 in metsuke-weight (weight per unit area), and 40-50 Kgf/5cm in fracture strength is used. Each of the partition walls 14 made of such material is provided with three or four circular air passage holes 17 along its length so that mutually adjacent cells 15 communicate with each other through these holes 17. For the purpose of reinforcing the partition wall 14, woven belts 18 are sewn to the partition wall 14 between the holes 17 along the height of the partition wall 14. A lower end of each belt 18 serves as a securing portion 19 for the suspension line 11. Due to the provision of the air passage holes 17 in the partition walls 14, if any of air intake 16 is still closed during the inflation, the air introduced through the other opened air intakes inflates all of the cells 15 through the air passage holes 17, thereby uniformly inflating and maintaining the entire canopy 10 in the wing-like shape.
However, when the paraglider takes off, tension is applied on the partition walls 14, especially, in the direction of the height thereof due to the internal pressure of the introduced air within the canopy 10 acting thereon, and the weight of the flyer transmitted thereto through the suspension lines 11 and the securing portions 19. Therefore, since each of the partition walls 14 is formed with the air passage holes 17, the tension causes stress concentration near the air passage holes 17 to deform the partition walls 14. As a result, it is difficult to maintain the partition walls 14 in a proper wing-like shape, and sufficient aerodynamic lift cannot be obtained. Thus, the conventional partition wall arrangement has a problem in that rapid lift cannot be performed.
On the other hand, for the purpose of securing sufficient strength in the partition wall 14, the formation of each of the air passage holes 17 in each partition wall 14 is restricted such that the area of the air passage holes 11 is not greater than 20% of the area of the partition wall 14. Accordingly, particularly when the wind is weak, another problem arises in that much more time is required to inflate the entire canopy 10 by introducing air through the air passage holes 17. Further, when turning the paraglider while gliding in the air, a control line 20, which is coupled to the trailing edge of the canopy 10, is pulled downwardly so as to slightly fold the canopy downwardly like a flap of an airplane. Therefore,
if the air communication through the air passage holes 17 is insufficient, a substantial amount of time is required to return the partially folded shape of the canopy to the original wing-like shape after completing the turn. As a result, it is impossible to control the paraglider promptly and the paraglider may experience a stall.